AUSTRALIA is preparing to take part in its biggest national survey and answer the important questions on the 2016 Census.

The Census has provided a snapshot of Australian life for more than a century - the most realistic image available to us of who and where we are on a single night.

This year, that night is just one sleep away.

About 10 million households and 24 million people are expected to be included in the national survey this year, making it the largest Census to date.

The Australian Bureau of Statistics takes the count every five years and uses the data to help all tiers of government decide where and how taxpayers' money should be spent.

The data is also used to help organisations in the public and private sectors make decisions on policy and planning that impact the lives of Australians.

Questions cover characteristics such as marriage status, family size and make-up, jobs, languages spoken, country of birth and ancestry.

Groups such as Australian Marriage Equality are urging people to answer the forms truthfully - in this case, so the government and other organisations have a true concept of how many same-sex couples live in Australia today.

More than 65% of households are expected to complete the Census online this year, through which the ABS says taxpayers will save more than $100 million.

Households should have started receiving letters from the ABS addressed "To the resident" from the beginning of August containing a unique 12-digit code and instructions on how to complete the survey online.

To request a paper version of the Census, residents must phone the ABS and quote the same 12-digit code.

The Census is supposed to uncover details about every person in every household on a particular night, so anyone staying with friends or a different residence will have to be included on that home's form.

Census officers will also canvass places such as caravan parks in remote areas to ensure people do not shirk their responsibilities.

In previous years, the numbers are thought to have been skewed by as much as 10% in some northern and remote areas through a lack of participation.

Hotel and other accommodation managers should supply guests with the forms when they check in.

Failing to fill out the Census can result in a $180 fine for each day until it is completed, although warnings are first issued and fines are considered a last resort.

Concerns have been raised about privacy since the ABS will keep names and addresses on record for up to four years this time around - an increase from 18 months in 2011.

The ABS has tried to assure Australians their identifying information would be protected.

"Other government agencies, private agencies and direct marketing companies will not have access to personal information that you provide on the Census form," its website states.

"This is protected by law.

"The 2016 Census is not asking for any additional personal information not provided in the previous Census."